Antenna switches are used in communication devices where switching between a receive and a transmit mode is required. In general, switching is accomplished via pin diodes. A pin diode is a specialized microwave diode which has an ON mode, when the diode is forward biased, and an OFF mode, when the diode is reverse biased. In the OFF mode the diode exhibits a high impedance, while in the ON mode it exhibits a low resistive impedance, where the resistance is proportional to the current through the device.
In the ON state, the diode draws a considerable amount of current. In systems with low power requirements, or in portable devices where power is of premium value, this high ON current can become a significant burden, the elimination of which is highly desirable. As an alternative, designers have turned their attention to GaAs switches in order to combat the high current consumption of pin diodes. These switches are, however, expensive and do not provide sufficient benefits to antenna switches to justify their high costs.
Another problem with pin diodes is the non-linear behavior of their p-n junction which is a significant problem under large signal conditions. A trend toward integration of communication devices has placed a significant demand for antenna switches to be integrated. Pin diodes can't be integrated and have, therefore, prevented the total integration of antenna switches. The non-linearity of pin diodes along with their lack of integratability added to their high current consumption has created a need for a low cost antenna switch which overcomes the deficiencies of the prior art.